GB2282900A

GB2282900A - Controlling an element influencing vehicle engine power

Info

Publication number: GB2282900A
Application number: GB9420296A
Authority: GB
Inventors: Reinhard Pfeufer; Thomas Frey; Johannes Wehle
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1993-10-12
Filing date: 1994-10-07
Publication date: 1995-04-19
Anticipated expiration: 2014-10-07
Also published as: GB9420296D0; DE4334720B4; FR2711184A1; DE4334720A1; GB2282900B; US5584272A; FR2711184B1

Abstract

A system to control an electrically actuable power-setting element in a vehicle eg a throttle, which element is set on the basis of a preliminary value DKV, comprises a procedure for adjusting the relationship between the preliminary value DKV and the actual value DKI of the element. In this procedure the element is set, in a predetermined engine operating state, according to a preset preliminary value DKV(VL) which does not correspond to the engine full load position of the element and according to further preset preliminary value DKV(LL) which does not correspond to the engine idling setting of the element. The corresponding actual values DKI(VL), DKI(LL) of the element are detected and processed together with the preliminary values and ideal values to derive a correction characteristic curve for the preliminary values. The predetermined operating condition can be the first engine start following disconnection of the battery. <IMAGE>

Description

2282900 METHOD OF AND CONTROL MEANS FOR CONTROLLING AN ELEMENT INFLUENCING

VEHICLE ENGINE POWER The present invention relates to a method of and control means for controlling an element influencing engine power in a vehicle.

In DE-OS 3 510 176 (US Patent 4 622 936) there is disclosed a method and a device for the control of setting equipment in the form of a power-setting element, preferably a throttle flap, of an internal combustion engine, which element is set in dependence on operating magnitudes, particularly the setting of a control member actuable by the vehicle driver. There, the problem is addressed that, for accurate control of the power-setting element, an exact association of the wish of the driver and the throttle flap setting is required. This association can change as a function of time due to ageing phenomena or example scatter or other inaccuracies caused by mechanical tolerances and adjustments. To sQlve this problem it is proposed that the mechanical abutments of the power-setting element, namely an idling abutment and a full load abutment, are detected continuously by a learning process and the association between the setting of the control member and a target value derived therefrom for the power-setting element is adapted appropriately. A regulator then sets the power-setting element according to the 20 target value.

is f.

Although this association can be balanced by this procedure, an adaptation of the target value and the actual value of a transmitter detecting the actual setting of the power-setting element, i.e. a compensation of the regulator for the setting of the power-setting element, cannot be effected in this manner. This compensation is achieved in conventional systems by compensating resistors in conjunction with the production of the control device, which leads to increased labour, increased costs and exposure to additional sources of error. Moreover, the abutments are frequently impacted in the known manner of procedure, whereby mechanical damage is possible.

There is therefore a need for measures by which the compensation of, in particular, a power-influencing element of an engine, is improved.

According to a first aspect of the invention there is provided a method of controlling an electrically actuable element influencing engine power in a vehicle, the element being settable in dependence on a preliminary value for and an actual value of the setting of the element, wherein the method comprises the step, in a predetermined operating state of the engine, of adjusting the relationship of the preliminary value and the actual value by way of a procedure in which the element is initially set in accordance with a first predetermined preliminary value differing from the value denoting one end position of the element and subsequently set in accordance with a second predetermined preliminary value differing from the value denoting the other end position of the element.

1 4 According to a second aspect of the invention there is provided control means for controlling an electrically actuable element influencing engine power in a vehicle, comprising means for - in dependence on a preliminary value for and an setting the element actual value of the setting of the element and means operative, in a predetermined operating state of the engine, to adjust the relationship of the preliminary value and the actual value by way of a procedure in which the element is initially set in accordance with a first predetermined preliminary value differing from the value denoting one end position of the element and subsequently set in accordance with a second predetermined preliminary value differing from the value denoting the other end position of the element.

Compensation for the setting of an element, in particular a power-setting element, in a control system may be appreciably is improved by such a method and control means. Inaccuracies and example scatter of electrical and mechanical components, and inaccuracies arising in consequence of their adjustment, can be compensated for. Moreover, the use of highly accurate measuring means for the compensation can be dispensed with. An exact matching of the target value for the setting of the element with the measured actual value can be achieved, which leads to accurate compensation of a position regulator for setting the element.

The method has particular advantages in conjunction with analog position regulators for the setting of the element, wherein the target value is preliminarily set by computing means. However, corresponding advantages are also achievable in conjunction with digital position regulators.

It is particularly advantageous that the compensation of the or each actual value transmitter for the setting of the element and the compensation of an associated position regulator can be dispensed with, so that costs savings can be achieved in the production of engine control devices and the mechanical components. Not only cheaper components can be used, but fewer components are needed. Furthermore, the number of the error sources is reduced.

It is also of advantage that an exact positioning of the element can be achieved in the zero point by incorporation of a learning process, so that accurate adjusting of the setting of the element for an available idling regulation is made possible.

For preference, the method is performed to the full extent only when the control means is put into operation for the first time after interruption of its supply voltage. Expediently, the engine operating state when the method is performed is first start-up of the engine after interruption of current supply to control means of the engine, after elapsing of a predetermined engine operating time, after attainment of a predetermined travel distance of the vehicle or after externally applied input into the control means.

The set values of the element, which are preliminarily set for an ideal case, can be positioned by a method exemplifying the invention so that an exact setting of the element is achievable without positional deviations from the ideal values.

The method is advantageous not only for a power-setting element of an internal combustion engine, such as a throttle flap or diesel injection pump, but also in conjunction with other setting devices in vehicles.

1 1.

An example of the method and embodiment of the control means of the present invention will now be more particularly described with reference to the accompanying drawings, in which:

Fig. 1 is a schematic block diagram of a controlsystem for the setting of a power-setting element for an internal combustion engine; Fig. 2 is a flow chart illustrating steps in a method exemplifying the invention; Fig. 3 is a flow chart illustrating steps in the determination of a target value after performance of a compensating procedure of the method; Fig. 4 is a set of diagrams showing signal courses arising during performance of the method; and Figs. 5 and 6 are diagrams showing slope characteristics applicable to the method.

Referring now to the drawings there is shown in Fig. 1 an overall block schematic diagram for a control system for the setting of a setting device, namely a power-setting element, of an internal combustion engine in a vehicle. In the systems, a control unit, which comprises at least one computer together with storage elements, is denoted by 10. The control unit 10 is supplied with voltage from a battery 14 by way of a line 12 connected to the 4 positive pole of the battery) the negative pole of which is earthed by a 1 ine 16. Input lines 18 and 20 to 22 of the control unit 10 connect the unit with at least one measuring device 24 for detection of the setting of a control member actuable by the vehicle driver and with measuring devices 26 to 28, for detection of further operating magnitudes of the engine 'and/or vehicle, which are required for the control of the engine. In addition, a further input line 30 of the control unit 10 connects it with at least one measuring device 32 for detection of the setting of a setting device 34, which is a power-setting element 34 in the preferred example of the method. An output line 36 of the control unit 10 leads to a regulator unit 38, to which is also connected a branch line 40 from the line 30. An output line 42 of the regulator unit 38 leads to the power-setting element 34, in particular an electrical setting motor 44, thereof. This is connected by way of a mechanical connection 46 on the one hand with the measuring device 32 and on the other hand with an actual power-setting member 48, which in this example is a throttle flap arranged in an induction duct 50 of the engine. The setting member 48 can be moved between two end positions respectively defined by two abutments, namely a minimum or lower abutment 52 (idling abutment) and a maximum or upper abutment 54 (full load abutment). The end positions are indicated in Fig. 1 by the positions of the setting member 48 shown in dashed lines.

In operation, the control unit 10 forms a target set value for the power-setting element 34, thus the setting member 48, in dependence on the setting of the control member, thus in dependence - 7 4 on the wish of the driver, communicated by way of the line 18 and, as required, subject to consideration of further operating magnitudes communicated by way of the lines 20 to 22. These further operating magnitudes are, for example, rotational speed of the engine, engine temperature, battery voltage, vehicle travel speed, vehicle gear and so forth. The translation of the wish of the driver into a target value is effected in a characteristic field which presets the interrelationship of the wish of the driver and the setting of the power-setting element in dependence on the operating magnitudes with a view to maximum torque, minimum fuel consumption and so forth. The target or preliminarily set value DKV is delivered by way of the lines 36 to the regulating unit 38. In the preferred example, this is an analog position regulator with proportional, integral and/or differential behaviour. The regulator forms an output signal, which actuates the setting motor 44 by way of the line 42, in dependence on the preliminary value DKV and the actual value DKI, which is detected by the measuring device 32, for the actual setting of the power-setting member 48. In that case, the drive control signal magnitude for the setting motor 44 is determined, as known from the regulation technology, on the basis of the difference between the preliminary value DKV and the actual value DKI in the sense of an approximation of the actual value to the preliminary value.

Since, as explained above, the preliminary value DKV is preset at least in dependence on the wish of the driver and represents a set position of the setting member 48 of the power-setting element A 34, the actual value of which is detected by the measuring device 32, it is necessary that the association between the preliminary value DU and the measured actual value DKI is adjusted. Thi s association is dependent on the tolerances of the electrical components of the regulator unit 38, the signal lines, the measuring device 32 and the setting motor 44 and on the mechanical tolerances in the region of the power-setting element 34. Furthermore, this association can be influenced by temperature influences, ageing phenomena and so forth. Accordingly, the regulator 38 or the measuring device 32 is compensated for by compensating resistors in known systems for the compensation of these inaccuracies so that, on preliminary setting of a certain DU value, the power-setting element 34 or the setting member 48 is led, independently of the tolerances, approximately into the position represented by the DKV value. In order to be able to dispense with the compensating process, the detected actual value DKI is fed by way of the 1 i ne 30 to the control unit 10, which on the basis of the preliminary value M and the actual value DKI ascertains a correction characteristic with a relationship between a target set value DKVKF, which is ascertained from a characteristic field on the basis of the wish of the driver, and the preliminary value M to be delivered, which drives the setting element so that the setting of the power-setting element 34 corresponds to the position represented by the DKVKF value.

Apart from the illustrated preferred example with an analog position regulator and the setting of a throttle flap, the manner of procedure according to the invention is applicable in other advantageous examples in conjunction with a digital regulator, which is accounted for in the control unit 10, and also with a powersetting element of a diesel engine, in particular the regulating rod of an injection pump. When several measuring devices, which are redundant one relative to the other, are provided, for the detection of the setting of the power-setting element 34, the method can be applied to each measuring device so that a correction characteristic is ascertained for each measuring device.

The method known from the initially mentioned state of the art is applied for ascertaining the exact position of the lower abutment 52, for which purpose the setting member 48, in predetermined is operating states, in particular before starting of the engine, is guided against this abutment according to a preset slope through actuation of the setting motor 44. The driving against the abutment is recognised by reference to the regulator output signal on the line 42 and the then present preliminary value (DKVUA) is stored as representing the lower abutment.

The procedure illustrated with the aid of a flow chart in Fig.

2 is followed on each starting of the combustion engine as initiated by a closing of the ignition switch. In that case, it is questioned in a first step 100 whether an "original" start is present. An "original" start is defined as start-up of the engine after the voltage supply of the control equipment has been interrupted, i.e.

A the battery has been disconnected. This has the consequence in control units with inscribable storage elements, which do not retain stored information when the voltage supply is interrupted that all storage content is erased, including the compensation values or correction characteristic ascertained as described in the following. Thus, a new compensation of the system is necessary with each such original start. In the case of control units with storage elements which retain the stored information even in the case of a voltage failure, the procedure illustrated in Fig. 3 need be performed only during the production of the vehicle, on change of components or at preset inspection intervals. In this case, it is interrogated in step 100, whether for example, a predetermined operating duration of the engine has been reached, a predetermined travel distance of the vehicle has been covered, external information, for example from a diagnostic device or a manually actuable switch has been applied, or the afore-mentioned original start has taken place.

If such a condition, such as an original start, has been recognised in step 100, for example by reference to a mark, a preliminary set value DU(VL) is delivered in a step 102 following therefrom. This val.ue lies in the region of that for full load abutment of the power-setting element, but is chosen in such a manner that the mechanical abutment is not actually reached. In a preferred example, this preliminary value lies at 85% of the value range, which extends from 0 to 100%, of the preliminary set values.

After lapse of a predetermined time duration, which the position regulator needs for the setting of the preliminary value, the - 11 measured actual value DC(VL) associated with this preliminary set value is entered into storage in a step 104 following thereupon. Thereafter, a preliminary set value MV(LL) lying in the region of that for the lower abutment is delivered in a step 106. As it, the case of the preliminary full load value, this value lies in the region of the lower abutment, but is selected so that the mechanical abutment of the power-setting element is not reached. In a preferred example this preliminary value WV(LL) lies at 15%. In other examples, these values can be chosen in advantageous manner between 5 and 30% or between 50 and 90%, respectively, it being important only that the mechanical abutments are not reached. After the end of the regulating time, the measured actual value DKI(LL) associated with the preliminary value WV(LL) is entered into storage in a step 108 following thereupon.

Apart from these values, an ideal characteristic of the association of the preliminary set -valtfe with the actual value is filed in the control unit. In that c.ase, an ideal value, which is fixedly preset, is associated (in the preferred example 15 and 85%) with the preliminary values delivered in steps 102 and 106. Since, in the preferred example, a so-called counter-running setting transmitter is used, in which the measurement signal value becomes lower with increasing opening of the setting member 48, these ideal setting values for the value WV(VL) are smaller in amount than for the value WV(LL). The ideal set values for both the drive control points are entered into storage in a step 110. In that case, in the preferred example, the associated ideal value DC(VL) ideal is 15% d( is for a value DOM) of 85%, whilst the ideal value DKI(LL) ideal amounts to 85% for the value DO(LL) of 15%. Through the preset preliminary values and the ideal values, an ideal characteristic of the system is spanned, which is subjecz to a correction line to be ascertained so that the set value DKI ideal derived from the ideal characteristic sets in at the setting member on delivery of a preliminary value D0U. In that case it is immaterial whether the course of the setting measurement values is chosen to be counterrunning as in the preferred example or co-running as in other advantageous examples.

After reading-in of the ideal values in step 110, the correction line is ascertained in a step 112. This takes place by means of known straight form equations on the basis of the preliminary values DU(VL) and DO(LL), the measured actual values DKI(VL) and DKI(LL) and the associated ideal values. The slope V and the axis intercept 0 of the correction characteristic in the preferred example are obtained by the following equations:

DKIM)ideal - DKI(LL)ideal ------ ----------------------DKI(VL) - DKI(LL) DKI(VL)-DKI(VL)ideal 0 ----------- DKV(LL) + DKI(VL) DKI(LL) (1) DKI(LL)ideal-DKI(LL) DKI(VL) - DKI(LL) DKV (VL) (2) The correction characteristic then results for the value DOU ascertained from the characteristic field as:

DU = V DOU + 0 (3) Moreover, the set value D00A associated with the upper abutment, namely the full load abutment, of the power-setting element can be estimated on the basis of the correction line in advantageous manner in the step 112.

Thereafter, the learning process known from the state of the art for exact detection of the lower abutment value DOUA is initiated according to a step 114. The step 114 is also initiated when it was recognised in step 100 that an original start, and none of the other conditions (if any) to be interrogated, was present.

This leads, in a step 116, to the deduction that a normal start is present and the correction characteristic does not thus have to be ascertained, but is taken over or stored.

During the learning process in step 114, the power-setting element is led, according to a slope, in direction of the mechanical abutment until contact with this abutment is recognised by reference to the regulator output signal. The then present value DGUA is detected in a step 118 and the associated set value DOUA is ascertained on the basis of the correction characteristic. Thereafter, the procedure is terminated and repeated on each new start of the engine.

The preliminary values associated with the two abutments serve for determination of the target setting range of the power-setting element according to real conditions.

Apart from the illustrated performance of the procedure on engine start-up in one or more predetermined conditions, the learning process can be performed in overrun operation.

The procedure for determination of a preliminary value with the use of a correction characteristic is illustrated in Fig. 3.

After the start of the procedure illustrated in Fig. 3 at preset times or at preset crankshaft settings, the driver wish (beta), which in the preferred example corresponds to the setting of the acceleration pedal, as well as optionally also further operating magnitudes, such as engine rotational speed n, engine temperature, battery voltage, gear setting and so forth, are entered into storage in a first step 200 and the preliminary set value DKVKF is read out of apreset characteristic field or from a preset characteristic on the basis of the read-in magnitudes, as known from the start of the art, in a step 202 following thereupon. The characteristic field in that case shows the dependence of the preliminary value DKVKF on the wish of the driver, for which different dependencies are preset for different rotational speeds of the engine or gear settings and so forth.

After reading-out of the preliminary value DKVKF, the preliminary value DKV to be delivered is computed in a step 204 on the basis of the ascertained correction characteristic according to equation (3) and in a given case limited to the upper value DKVOA or 1 A the lower value DMA. The computed preliminary value DU is then delivered to the position regulator according to step206.

Thereafter, the procedure is terminated.

Fig. 4 shows the procedure with the aid of a time diagram for the setting of the power-setting element. In that case, the switching signal of the ignition switch is entered in Fig. 4(a), the actual setting value DKI of the power-setting element is illustrated as a function of time in Fig. 4(b), and the course of the preliminary value D0 is shown as a function of time in Fig. 4(c).

The ignition switch is closed at an instant T1, which in the case of an original start or a different condition leads to the delivery of the preset preliminary value DU(VL). The power-setting element is moved by the position regulator out of a rest position to a position in which the actual value DKI(VL) can be detected and is then stored. At the instant T2, at which the power-setting element by reason of the dynamics of the system has reliably reached the position associated with the preliminary value DU(VL), the preset preliminary value DO(LL) is then delivered, which leads to a drive of the power- setting element into the position at which the associated actual value DKI(LL) can be detected. This detected value is also stored, whereupon the correction line according to the equations (1) and (2), and optionally also the upper abutment value D00A, are computed and the learning process is initiated at the instant T 3 The preliminary value D0 is displaced at a preset slope until recognition of drive against the lower abutment. The then present lower abutment value DOUA is determined and stored.

A At the instantT 4 ' the learning process is terminated and the powersetting eiement is led to its start setting and the engine is started. If an original start is not present, the illustrated The time durations in that case are preset in such a manner that attainment of the intended position of the power-setting element and completion of the necessary computations is ensured each time. Furthermore, in other advantageous examples, the learning process can be dispensed with or can be performed at another point in time independently of the procedure for ascertaining the correction characteristic.

Fig. 5 shows the relationship between the correction characteristic and the ideal characteristic. In that case, the correction characteristic is entered in the lower part of the diagram, wherein the value DKVKF ascertained in dependence on at least the wish of the driver is represented vertically and the preliminary value DKV to be delivered is represented horizontally. In the upper part of the diagram, the set value DKI is entered as preset ideal characteristic as a function of the preliminary value DKV. The correction in that case is determined in such a manner that the ideal value DKI(LL)id of 85% arises for a preliminary value DKVKF, for example, 15%. The same applies for a presetting of 85%, for which the ideal value DKI(VL)id of 15% arises.

The correction characteristic is accordingly so determined that the respective ideal set value sets in for each of the preliminary values DKV(VL) and DKV(LL) of 85% and 15%, respectively. This means that the correction characteristic contains a correction procedure is performed onward from the instant T 3 t 4 of the preliminary set value DKEF in such a manner that the ideal characteristic of the setting of the power-setting element DKI sets in by way of the preliminary value D0 fed to the position regulator.

The effect of the manner of procedure is illustrated in different manner in Fig. 6. The diagram shows the set value OKI entered as a function of the preliminary value DU. In that case, the preliminary values DO(LL) of 15% and DC(VL) of 85%, which in this example correspond to actual values DKI(LL) of 90% and DC(VL) of 8%, respectively, are delivered for the formation of the correction line. These preliminary values are, however, associated with the idal setting values DKI(LL)id of 85% and DC(VL)id of 15%. Through computation of the correction line, these values are set for a preliminary setting of DOU of 15% and 85%, respectively, i.e. a preliminary value D0 corrected according to equation (3) is delivered for the setting of the value 15%. Analogously, a corrected preliminary value D0 corr is delivered for the setting of the value 85%. In this manner, it is possible, by correction of the preliminary values, to realise an ideal preset characteristic with the aid of the dependence of the set values on the preliminary val ue.

4

Claims

1. Method of controlling an electrical I y actuable element influencing engine power in a vehicle, the element being settable in dependence on a preliminary value for and an actual value of the setting of the element, wherein the method comprises the step, in a predetermined operating state of the engine, of adjusting the relationship of the preliminary value and the actual value by way of a procedure in which the element is initially set in accordance with a first predetermined preliminary value differing from the value denoting one end position of the element and subsequently set in accordance with a second predetermined preliminary value differing from the value denoting the other end position of the element.

2. A method as claimed in claim 1, wherein the first preliminary value lies in the region of the value denoting an element end position for engine full load and the.second preliminary value lies in the region of the value denoting an element end position for engine idling.

3. A method as claimed in claim 1 or claim 2, comprising the steps of detecting the actual values when the element is in the settings produced by the first and second preliminary values and processing the detected actual values, the respectively associated preliminary values and predetermined ideal values to obtain a correction characteristic curve for all preliminary values such that on reading out of a preliminary value for setting of the element the associated ideal value is generated.

4 4. A method as claimed in any one of the preceding claims, wherein the preliminary values are target values of a position regulator regulating the setting of the element.

5. A method as claimed in any one of the preceding claims, comprising the further step, in said operating state, of determining preliminary values and actual values associated with the end positions of the element, the end positions being fixed by mechanical stops.

6. A method as claimed in claim 5, wherein the end positions are respectively associated with engine idling and engine full load and the step of determining the preliminary value associated with the end position for engine idling is carried out by a learning process.

7. A method as claimed in claim 5, when appended to claim 3, wherein the end positions are respectively associated with engine idling a. nd engine full load and the step of determining the preliminary value associated with the end position for engine full load is carried out by computation from the correction characteristic curve.

8. A method as claimed in claim 4, wherein the regulator is an analog regulator.

9. A method as claimed in any one of the preceding claims, wherein said operating state is first start-up of the engine after interruption of current supply to control means of the engine, after elapsing of a predetermined engine operating time, after attainment of a predetermined travel distance of the vehicle or after externally applied input into the control means.

10. A method as claimed in claim 6, comprising the further step, in the absence of said operating state, of re-determining the preliminary value associated with the end positions for engine idling by a learning process carried out on each start-up of the engine.

11. A method as cl aimed in cl aim 1 and substantially as hereinbefore described with reference to the accompanying drawings.

12. Control means for controlling -an electrically actuable element influencing engine power in a vehicle, comprising means for setting the element in dependence on a preliminary value for and an actual value of the setting of the element and means operative, in a predetermined operating state of the engine, to adjust the relationship of the preliminary value and the actual value by way of a procedure in which the element is initially set in accordance with a first predetermined preliminary value differing from the value denoting one end position of the element and subsequently set in accordance with a second predetermined preliminary value differing from the value denoting the other end position of the element.

i

13. Control means substantially as hereinbefore described with reference to the accompanying drawings.

14. A motor vehicle provided with an electrically actuable ellement for influencing the power of the vehicle engine and control means as claimed in claim 12 or claim 13 for controlling the element.

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